What is Dengeki?
Dengeki is a website (it's also a brand of magazines / a book and manga imprint) that publishes sell-through Japanese sales data tracked by Kadokawa ASCII Research Laboratories, Inc., a division of Kadokawa Corporation. Every week they publish a nationwide snapshot of Japanese video game sales with the cooperation of more than 3,000 specialty game stores and convenience store chains all across Japan.

Why post Dengeki numbers when you have Media Create / Famitsu in the OP?
1) Unlike any other tracker, Dengeki gives us software numbers for Top 50 sales so we can track low-performing titles for a longer period of time
2) Unlike the others, Dengeki gives us total software sales for every platform, so we can track the relative health of platform software ecosystems
3) Dengeki is a respected sales tracker with 5 consecutive years of being reported each week in GAF threads

Is Dengeki less accurate than Media Create / Famitsu?
1) Dengeki is just as accurate as Media Create and Famitsu. Just because each tracker has quirks and natural deviations from the others doesn't mean one is inherently superior to the rest.
2) Dengeki is the tracker most unfamiliar to GAF / the public, and sometimes people confuse lack of dissemination with inaccuracy in sales figures
3) The amount of retail stores Dengeki tracks is similar to Media Create and Famitsu

Famitsu:
+ Nationwide Japanese sales data from Enterbrain, Inc.
+ Tracks about 3,600 retail stores / chains
+ Top 30 software sales with numbers
+ Total hardware sales per platform
+ Sell-through ranges for all titles
+ Has the most historical data available for GAFfers
+ Tracks download cards
+ Releases first (at the same time as Media Create)
- Does not distinguish between 3DS and 3DS LL
- Does not distinguish between Vita and Vita TV
- Does not report total software sales